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M J Lyons

Publications and source records attributed to M J Lyons.

100 records · Page 6Linked to original sources
PubMed1965

Phase-contrast and electron microscopy of murine strains of Mycoplasma.

Nelson, John B. (The Rockefeller University, New York, N.Y.), and Michael J. Lyons. Phase-contrast and electron microscopy of murine strains of Mycoplasma. J. Bacteriol. 90:1750-1763. 1965.-Two strains of Mycoplasma pulmonis (associated with infectious catarrh) on examination in fluid culture (20% horse serum-bouillon) by phase microscopy were highly pleomorphic, with many bacilliform elements and fewer coccoid ones. Motility, characterized by gliding of rods and spinning of spherical forms, was observed through the 9th subculture of one strain and the 15th of the second. Motile elements were not seen in later transfers and pleomorphism was reduced. One strain of M. neurolyticum (associated with conjunctivitis and encephalitis) was much less pleomorphic and showed neither bacilliform elements nor motility at any time. When examined by negative-contrast electron microscopy, organisms of this strain were found to have an average diameter of 0.7 mu and to possess a concentrated peripheral layer of cytoplasm and a central mass which may represent the cells' nuclear equivalent. The latter feature was not prominent in spherical forms of M. pulmonis. These cells, when observed after 48 hr of culture, showed evidence of the generation of new progeny cells in their central area. The filamentous or bacilliform cells of M. pulmonis were frequently serpentine in appearance, 2.0 to 3.0 mu in length and 80 to 250 mmu in width. They appeared to generate new cells from terminal buds from which outpouchings initially developed. Older cells, in the stationary phase, showed evidence of undergoing multipolar germination. Microtubules, about 60 mmu wide, were found in association with most filamentous cells from 48-hr cultures; fragments of membrane, studded with closely packed ribosomelike particles, were also found. There was no evidence of flagella or any specialized structure that could account for the observed motility of the organisms.

Animals↗
PubMedDate not supplied

The relationship between DSM-III personality disorders and the five-factor model of personality.

Two hundred twenty-four first-degree relatives of patients with psychotic disorders were administered the Structured Interview for DSM-III Personality Disorders (SIDP) and completed a self-report instrument to assess dimensions of the five-factor model of personality. All of the DSM-III personality disorders were related to one or more dimensions of the five personality factors; however, the correlations were generally low. It seems that the five personality factors describe important features of DSM-III personality disorders, but are not sufficient to completely explain their characteristics. Future use of the five-factor model in conjunction with personality disorder diagnoses may provide useful information for clinical work and research purposes.

Adolescent↗
PubMedDate not supplied

Empirical determination of thresholds for case identification: validation of the Personality Diagnostic Questionnaire-Revised.

The Personality Diagnostic Questionnaire-Revised (PDQ-R) was sent to first-degree relatives of major psychotic patients for identification of DSM-III-R personality disorders (PDs). Responses to the PDQ-R were interpreted both literally and empirically, and compared with the Structured Interview for DSM-III PDs (SIDP) as the standard. For literal interpretation, symptoms reported were counted directly for case identification using fixed DSM-III-R thresholds. The empirical approach adjusted the threshold for case identification to maximize concordance with the SIDP. Comparison of the two methods showed that using empirically determined thresholds in some scales gives better concordance with the SIDP. For the dependent and histrionic PD scales, the improvements were statistically significant. The area under the receiver operating characteristic (ROC) curve was computed for each PDQ-R scale to summarize its discriminatory capability across all thresholds. Areas under the ROC curve indicated that the schizoid, schizotypal, borderline, dependent, passive-aggressive, and histrionic PD scales in the PDQ-R have better discriminatory qualities than other PDQ-R scales.

Adult↗
PubMedDate not supplied

Familial and sporadic schizophrenia. A simulation study of statistical power.

The importance of genetic factors in schizophrenia is clear but the mechanism involved remains obscure. Etiological heterogeneity may be responsible. Recently there has been interest in a putative distinction between genetic and environmental forms of the illness based on a positive or negative family history of the disorder. Those with a positive family history are classified as 'familial' and are considered to be more likely to have the genetic form of the illness. Those with a negative family history are classified as 'sporadic' and considered more likely to have an environmental form of the illness. This paper reports the results of a Monte Carlo simulation study with varying rates of misclassification to determine the statistical power of comparisons between familial and sporadic groups. For a large sample (n = 175) statistical power was moderate to good for effect sizes greater than or equal to 1.0 standard deviation unit and positive predictive value of 0.3 or greater.

Humans↗
PubMedDate not supplied

Evidence for genetic influences common and specific to symptoms of generalized anxiety and panic.

BACKGROUND: Generalized anxiety disorder (GAD) and panic disorder (PD) often co-occur and have been shown to be heritable. Researchers have debated the validity of the distinction between GAD and PD. To test for distinction between disorders, we estimated the genetic and environmental contributions which were specific and common to GAD and PD in a cohort of male-male twin pairs. METHODS: Data were obtained from a telephone interview performed in 1992 utilizing the Diagnostic Interview Schedule Version 3-Revised. Interviews were administered to 6724 male-male monozygotic and dizygotic twin pair members of the Vietnam Era Twin Registry. We defined lifetime GAD by the report of six or more DSM-III-R symptoms and lifetime PD by the report of four or more DSM-III-R symptoms. RESULTS: The lifetime co-occurrence of GAD and PD was best explained by a model which did not include family environmental influences. The variance in risk for GAD was due to a 37.9% influence from additive genetic factors with the remainder due to unique environmental influences. The variance in risk for PD was due to a 22.6% additive genetic contribution which was common with GAD and a 21.2% non-additive genetic contribution specific to PD with the remainder of variance in risk for PD due to unique environmental influences. LIMITATIONS: Results may be limited to middle aged males. Model fitting with full diagnostic criteria was not possible due to low prevalences. CONCLUSIONS: Our data suggest a distinction in liability for GAD versus PD. The common genetic influence to GAD and PD may partially account for the risk of the co-occurrence of these disorders in a lifetime.

Age of Onset↗
PubMedDate not supplied

Contribution of emotionally traumatic events and inheritance to the report of current physical health problems in 4042 Vietnam era veteran twin pairs.

OBJECTIVE: To determine the contributions of psychological trauma (exposure to combat during the Vietnam War), genetic factors, childhood experiences shared by twin siblings, and unmeasured experiences not shared by twin siblings to the reporting of current physical health problems a mean of 19 years after military service. METHODS: In 1987, a national sample of 2224 monozygotic and 1818 dizygotic male veteran members of the Vietnam Era Twin Registry participated in a survey of health. Genetic modeling was performed on cross-sectional physical health and combat exposure data derived from Registry twins. RESULTS: Combat experiences explained a small proportion (0.7-8.4%) of the variance in the report of hypertension, respiratory conditions, persistent skin conditions, gastrointestinal disorders, joint disorders, and hearing problems. Childhood experiences shared by siblings are not clearly related to any health problem studied. By contrast, genetic factors explain 31 to 54% and noncombat experiences not shared by siblings explain 45 to 66% of the variance in current physical health status. CONCLUSIONS: Greater than 90% of the variance in reported current physical health problems in Vietnam era veterans is attributable to inherited factors and unmeasured environmental experiences not shared by twin siblings. The traumatic experience of combat makes only a small contribution to the report of current physical health problems. These results do not preclude the possibility that combat influenced the prevalence of illness shortly after military service or that combat may influence the development of illness in the future.

Adult↗
PubMedDate not supplied

The Harvard Twin Study of Substance Abuse: what we have learned.

The Harvard Twin Study of Substance Abuse was carried out with the members of the Vietnam Era Twin (VET) Registry. The VET Registry comprises over 8000 male twins who served in the United States military between 1965 and 1975 and were subsequently interviewed regarding their use of licit and illicit substances, as well as various types of psychopathology. Our research has demonstrated significant influences by genetic, shared environmental, and unique environmental factors on the abuse of illicit substances. Multivariate analyses have indicated that the co-occurrence of abuse of various types of illicit drugs reflects a common vulnerability, influenced by both genetic and environmental factors, that cuts across all categories of illicit drugs. We have also demonstrated that some drugs have unique determinants, both genetic and environmental, that are not shared with other drugs. In part, the genetic influence on marijuana abuse is mediated by genetic influence on subjective effects in response to the drug. The determinants of transitions from one stage of drug use to another differ depending on which drug or which transition is examined. We determined significant genetic influences on several aspects of nicotine and alcohol use separately, as well as genetic influences shared by both substances. We found that the co-occurrence of illicit drug abuse and major depression is due to unique environmental influences. The phenotypic association between symptoms of conduct disorder and alcohol and marijuana dependence is due largely to shared environmental influences. Our results, thus far, indicate a complex pattern of genetic and environmental influences on substance use and abuse.

Adult↗